I just ran VAINFO from the console and it returned this
LibreELEC:~ # vainfo
Trying display: drm
libva info: VA-API version 1.16.0
libva info: Trying to open /usr/lib/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_16
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.16 (libva 2.16.0)
vainfo: Driver version: Mesa Gallium driver 22.2.2 for AMD Radeon Graphics (renoir, LLVM 15.0.4, DRM 3.48, 6.0.6)
vainfo: Supported profile and entrypoints
VAProfileMPEG2Simple : VAEntrypointVLD
VAProfileMPEG2Main : VAEntrypointVLD
VAProfileJPEGBaseline : VAEntrypointVLD
VAProfileVP9Profile0 : VAEntrypointVLD
VAProfileVP9Profile2 : VAEntrypointVLD
VAProfileNone : VAEntrypointVideoProc
LibreELEC:~
It looks like it is missing the profiles for HEVC etc.